Promotive effect of auxins on UDP-glucose: flavonol glucosyltransferase activity in Vitis sp. cell cultures

Plants under Stress: Involvement of Auxin and Cytokinin

Plant growth and development are critically influenced by unpredictable abiotic factors. To survive fluctuating changes in their environments, plants have had to develop robust adaptive mechanisms. The dynamic and complementary actions of the auxin and cytokinin pathways regulate a plethora of developmental processes, and their ability to crosstalk makes them ideal candidates for mediating stress-adaptation responses. Other crucial signaling molecules responsible for the tremendous plasticity observed in plant morphology and in response to abiotic stress are reactive oxygen species (ROS). Proper temporal and spatial distribution of ROS and hormone gradients is crucial for plant survival in response to unfavorable environments. In this regard, the convergence of ROS with phytohormone pathways acts as an integrator of external and developmental signals into systemic responses organized to adapt plants to their environments. Auxin and cytokinin signaling pathways have been studied extensively. Nevertheless, we do not yet understand the impact on plant stress tolerance of the sophisticated crosstalk between the two hormones. Here, we review current knowledge on the function of auxin and cytokinin in redirecting growth induced by abiotic stress in order to deduce their potential points of crosstalk.

Production of Flavonoids in Organogenic Cultures of Alpinia Zerumbet

Alpinia zerumbet plantlets were cultured in vitro in MS medium supplemented with growth regulators, including IAA, TDZ and BAP. Using high performance liquid chromatography (HPLC), the production of rutin, kaempferol-3- O-glucuronide, and kaempferol-3 -O-rutinoside was evaluated, based on leaf hydroalcoholic extracts of three-month-old plantlets. The relative concentration of phenolics from the hydroalcoholic extracts of plantlets cultured in control medium reached 100% compared with plantlets treated with growth regulators and donor plants (80%). The in vitro rutin production was more pronounced than the other flavonoids. While no direct relation between the content of phenolic compounds and increased flavonoid production was observed, the combination of IAA + TDZ enhanced the production of rutin (83.2 μg/g dried leaves) and kaempferol-3- O-glucuronide (29 μg/g dried leaves), compared with growth regulators used alone. Overall, these findings suggest the value of in vitro cultivation as a means of enriching phenolic and flavonoid production in medicinal plants.